1. Field of the Invention
The present invention relates to a liquid ejecting device. More particularly, the present invention relates to a liquid ejecting device in which liquid droplets can be ejected in a regularly optimized amount or size.
2. Description Related to the Prior Art
An ink jet printer is known as an image forming device in which liquid is ejected. An ink jet printhead has an array of ejection nozzles for ejecting ink to recording material. An ink supply tank is incorporated the ink jet printer, and supplies the ink jet printhead with ink through an ink supply tube or supply path.
One type of the ink jet printer has the ink jet printhead movable up and down in the course of printing. In this type, water head pressure of the ink applied to the ejection nozzles is remarkably changed by the vertical movement of the ink jet printhead. A size in ink droplets ejected by the ejection nozzles changes to lower the image quality. In order to solve such a problem, a type of the ink jet printer disclosed in U.S. Pat. No. 6,220,700 (corresponding to JP-A 11-277768) has a pressure adjustor for adjusting the water head pressure of the ink according to a position of the ink jet printhead.
The water head pressure in the ink jet printer applied to the ejection nozzles changes also according to specific types of the ink. So known types of the ink jet printer has a short coming of degradation of image due to changes in the size of ink droplets ejected through the ejection nozzles. Failure may occur in ejection of ink. Furthermore, the supply tank may be refilled with ink in the course of recording one image, because the water head pressure change to lower the quality of the image. A more serious problem may occur in that there is a leakage of the ink to pollute the recording material.
It is necessary to control the water head pressure applied to the ejection nozzles according to types of the ink. However, the above-indicated prior document does not suggest countermeasures to changes in the water head pressure in consideration of the types of the ink or refilling of the ink. In the document, only the ink jet printer with the ink jet printhead movable vertically is disclosed. There is no known technique of keeping image quality by effectively considering changes in the water head pressure.
Also, the water head pressure of the ink is influenced by atmospheric pressure. To control the water head pressure with high precision, it is necessary to consider the total of the influence of the type of the ink, the atmospheric pressure and other important factors.